As is known, rail haul vehicles that draw current from an overhead contact line generally use a device, known as pantograph, to connect the line to the vehicle.
A pantograph is constituted by an articulated system, known as frame, which is mounted by means of isolators on the roof of the rail vehicle, and by a bow provided with gliding elements which are in direct contact with the wire or wires of the electrical contact line.
The gliding elements are constituted by bars of conducting material, for example copper, steel, aluminum or carbon. These gliding elements are subjected continuously to wear due to the mechanical friction induced during gliding along the contact line.
For correct operation of locomotives, it is important to monitor the state of wear of the gliding elements, so as to be able to repair or replace them when they are worn or damaged. A damaged or worn pantograph in fact can cause such damage both to the locomotive and to the overhead electrical line as to render the railroad line unusable until repaired.
For this reason, a manual inspection of pantographs is usually performed at regular intervals; this type of inspection requires the electrical isolation of the lines and access to the roof of the cars to be inspected; it is, therefore, an expensive method that is inefficient in terms of personnel work and in terms of time for which the cars are inactive.
In order to obviate the drawbacks associated with manual inspection, systems for automatic detection of the state of wear of pantographs are known in the art.
In particular, systems are known which incorporate optical fibers next to the gliding elements of a pantograph. Optical signals are transmitted in these optical fibers so as to be able to detect, if the optical signal is lost, any damage to a fiber and consequently obtain an indication related to the damage or excessive wear of the gliding elements. Although these systems are rather accurate in signaling problems to pantographs, they suffer the drawback of being prohibitive in terms of production costs.
An alternative approach adopted in more recent years consists in providing automatic monitoring systems: in these systems, digital images of the pantographs, captured while the trains pass, are analyzed automatically to determine whether there is damage to the pantographs or excessive wear of the gliding material and to optionally generate alarm messages. These systems are convenient in terms of installation and maintenance costs, but in the background art they have not yet reached a sufficient level of accuracy as regards image analysis techniques, with the consequence that the generated alarm messages are not always reliable. Moreover, in general these systems allow inspection of the pantograph only in controlled environments, in which the train passes at a limited speed and typically require an image acquisition infrastructure that comprises, in addition to a still camera, a synchronization system in order to manage image taking simultaneously with the passing of the train and a lighting apparatus, with a consequent increase in the complexity and costs of this equipment.